/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2019 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf.security;

import com.itextpdf.text.ExceptionConverter;
import com.itextpdf.text.error_messages.MessageLocalization;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.security.MakeSignature.CryptoStandard;
import org.bouncycastle.asn1.*;
import org.bouncycastle.asn1.cms.Attribute;
import org.bouncycastle.asn1.cms.AttributeTable;
import org.bouncycastle.asn1.cms.ContentInfo;
import org.bouncycastle.asn1.esf.SignaturePolicyIdentifier;
import org.bouncycastle.asn1.ess.ESSCertID;
import org.bouncycastle.asn1.ess.ESSCertIDv2;
import org.bouncycastle.asn1.ess.SigningCertificate;
import org.bouncycastle.asn1.ess.SigningCertificateV2;
import org.bouncycastle.asn1.gm.GMObjectIdentifiers;
import org.bouncycastle.asn1.ocsp.BasicOCSPResponse;
import org.bouncycastle.asn1.ocsp.OCSPObjectIdentifiers;
import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;
import org.bouncycastle.asn1.tsp.MessageImprint;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.cert.jcajce.JcaX509CertificateHolder;
import org.bouncycastle.cert.ocsp.BasicOCSPResp;
import org.bouncycastle.cert.ocsp.CertificateID;
import org.bouncycastle.cert.ocsp.SingleResp;
import org.bouncycastle.jce.X509Principal;
import org.bouncycastle.jce.provider.X509CertParser;
import org.bouncycastle.operator.DigestCalculator;
import org.bouncycastle.operator.jcajce.JcaDigestCalculatorProviderBuilder;
import org.bouncycastle.tsp.TimeStampToken;
import org.bouncycastle.tsp.TimeStampTokenInfo;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.*;
import java.security.cert.*;
import java.security.cert.Certificate;
import java.util.*;

/**
 * This class does all the processing related to signing
 * and verifying a PKCS#7 signature.
 */
public class PdfPKCS7 {

    // Constructors for creating new signatures

    /**
     * Assembles all the elements needed to create a signature, except for the data.
     * @param privKey the private key
     * @param certChain the certificate chain
     * @param interfaceDigest the interface digest
     * @param hashAlgorithm the hash algorithm
     * @param provider the provider or <code>null</code> for the default provider
     * @param hasRSAdata <CODE>true</CODE> if the sub-filter is adbe.pkcs7.sha1
     * @throws InvalidKeyException on error
     * @throws NoSuchProviderException on error
     * @throws NoSuchAlgorithmException on error
     */
    public PdfPKCS7(PrivateKey privKey, Certificate[] certChain,
                    String hashAlgorithm, String provider, ExternalDigest interfaceDigest, boolean hasRSAdata)
      throws InvalidKeyException, NoSuchProviderException, NoSuchAlgorithmException {
        this.provider = provider;
        this.interfaceDigest = interfaceDigest;
        // message digest
        digestAlgorithmOid = DigestAlgorithms.getAllowedDigests(hashAlgorithm);
        if (digestAlgorithmOid == null)
            throw new NoSuchAlgorithmException(MessageLocalization.getComposedMessage("unknown.hash.algorithm.1", hashAlgorithm));

        // Copy the certificates
        signCert = (X509Certificate)certChain[0];
        certs = new ArrayList<Certificate>();
        for (Certificate element : certChain) {
            certs.add(element);
        }


        // initialize and add the digest algorithms.
        digestalgos = new HashSet<String>();
        digestalgos.add(digestAlgorithmOid);

        // find the signing algorithm (RSA or DSA)
        if (privKey != null) {
            digestEncryptionAlgorithmOid = privKey.getAlgorithm();
            if (digestEncryptionAlgorithmOid.equals("RSA")) {
                digestEncryptionAlgorithmOid = SecurityIDs.ID_RSA;
            }
            else if (digestEncryptionAlgorithmOid.equals("DSA")) {
                digestEncryptionAlgorithmOid = SecurityIDs.ID_DSA;
            }
            else {
                throw new NoSuchAlgorithmException(MessageLocalization.getComposedMessage("unknown.key.algorithm.1", digestEncryptionAlgorithmOid));
            }
        }

        // initialize the RSA data
        if (hasRSAdata) {
            RSAdata = new byte[0];
            messageDigest = DigestAlgorithms.getMessageDigest(getHashAlgorithm(), provider);
        }

        // initialize the Signature object
        if (privKey != null) {
        	sig = initSignature(privKey);
        }
    }

    // Constructors for validating existing signatures

    /**
     * Use this constructor if you want to verify a signature using the sub-filter adbe.x509.rsa_sha1.
     * @param contentsKey the /Contents key
     * @param certsKey the /Cert key
     * @param provider the provider or <code>null</code> for the default provider
     */
    @SuppressWarnings("unchecked")
	public PdfPKCS7(byte[] contentsKey, byte[] certsKey, String provider) {
        try {
            this.provider = provider;
            X509CertParser cr = new X509CertParser();
            cr.engineInit(new ByteArrayInputStream(certsKey));
            certs = cr.engineReadAll();
            signCerts = certs;
            signCert = (X509Certificate)certs.iterator().next();
            crls = new ArrayList<CRL>();

            ASN1InputStream in = new ASN1InputStream(new ByteArrayInputStream(contentsKey));
            digest = ((ASN1OctetString)in.readObject()).getOctets();

            if (provider == null) {
                sig = Signature.getInstance("SHA1withRSA");
            } else {
                sig = Signature.getInstance("SHA1withRSA", provider);
            }

            sig.initVerify(signCert.getPublicKey());

            // setting the oid to SHA1withRSA
            digestAlgorithmOid = "1.2.840.10040.4.3";
            digestEncryptionAlgorithmOid = "1.3.36.3.3.1.2";
        } catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    /**
     * Use this constructor if you want to verify a signature.
     * @param contentsKey the /Contents key
     * @param filterSubtype the filtersubtype
     * @param provider the provider or <code>null</code> for the default provider
     */
	@SuppressWarnings({ "unchecked" })
	public PdfPKCS7(byte[] contentsKey, PdfName filterSubtype, String provider) {
        this.filterSubtype = filterSubtype;
        isTsp = PdfName.ETSI_RFC3161.equals(filterSubtype);
        isCades = PdfName.ETSI_CADES_DETACHED.equals(filterSubtype);
        try {
            this.provider = provider;
            ASN1InputStream din = new ASN1InputStream(new ByteArrayInputStream(contentsKey));

            //
            // Basic checks to make sure it's a PKCS#7 SignedData Object
            //
            ASN1Primitive pkcs;

            try {
                pkcs = din.readObject();
            }
            catch (IOException e) {
                throw new IllegalArgumentException(MessageLocalization.getComposedMessage("can.t.decode.pkcs7signeddata.object"));
            }
            if (!(pkcs instanceof ASN1Sequence)) {
                throw new IllegalArgumentException(MessageLocalization.getComposedMessage("not.a.valid.pkcs.7.object.not.a.sequence"));
            }
            ASN1Sequence signedData = (ASN1Sequence)pkcs;
            ASN1ObjectIdentifier objId = (ASN1ObjectIdentifier)signedData.getObjectAt(0);
            if (!objId.getId().equals(SecurityIDs.ID_PKCS7_SIGNED_DATA))
                throw new IllegalArgumentException(MessageLocalization.getComposedMessage("not.a.valid.pkcs.7.object.not.signed.data"));
            ASN1Sequence content = (ASN1Sequence)((ASN1TaggedObject)signedData.getObjectAt(1)).getObject();
            // the positions that we care are:
            //     0 - version
            //     1 - digestAlgorithms
            //     2 - possible ID_PKCS7_DATA
            //     (the certificates and crls are taken out by other means)
            //     last - signerInfos

            // the version
            version = ((ASN1Integer)content.getObjectAt(0)).getValue().intValue();

            // the digestAlgorithms
            digestalgos = new HashSet<String>();
			Enumeration<ASN1Sequence> e = ((ASN1Set)content.getObjectAt(1)).getObjects();
            while (e.hasMoreElements()) {
                ASN1Sequence s = e.nextElement();
                ASN1ObjectIdentifier o = (ASN1ObjectIdentifier)s.getObjectAt(0);
                digestalgos.add(o.getId());
            }

            // the possible ID_PKCS7_DATA
            ASN1Sequence rsaData = (ASN1Sequence)content.getObjectAt(2);
            if (rsaData.size() > 1) {
                ASN1OctetString rsaDataContent = (ASN1OctetString)((ASN1TaggedObject)rsaData.getObjectAt(1)).getObject();
                RSAdata = rsaDataContent.getOctets();
            }

            int next = 3;
            while (content.getObjectAt(next) instanceof ASN1TaggedObject)
                ++next;


            // the certificates
/*
			This should work, but that's not always the case because of a bug in BouncyCastle:
*/
            X509CertParser cr = new X509CertParser();
            cr.engineInit(new ByteArrayInputStream(contentsKey));
            certs = cr.engineReadAll();
/*
            The following workaround was provided by Alfonso Massa, but it doesn't always work either.

            ASN1Set certSet = null;
            ASN1Set crlSet = null;
            while (content.getObjectAt(next) instanceof ASN1TaggedObject) {
                ASN1TaggedObject tagged = (ASN1TaggedObject)content.getObjectAt(next);

                switch (tagged.getTagNo()) {
                case 0:
                    certSet = ASN1Set.getInstance(tagged, false);
                    break;
                case 1:
                    crlSet = ASN1Set.getInstance(tagged, false);
                    break;
                default:
                    throw new IllegalArgumentException("unknown tag value " + tagged.getTagNo());
                }
                ++next;
            }
            certs = new ArrayList<Certificate>(certSet.size());

            CertificateFactory certFact = CertificateFactory.getInstance("X.509", new BouncyCastleProvider());
            for (Enumeration en = certSet.getObjects(); en.hasMoreElements();) {
                ASN1Primitive obj = ((ASN1Encodable)en.nextElement()).toASN1Primitive();
                if (obj instanceof ASN1Sequence) {
    	            ByteArrayInputStream stream = new ByteArrayInputStream(obj.getEncoded());
    	            X509Certificate x509Certificate = (X509Certificate)certFact.generateCertificate(stream);
    	            stream.close();
    				certs.add(x509Certificate);
                }
            }
*/
            // the signerInfos
            ASN1Set signerInfos = (ASN1Set)content.getObjectAt(next);
            if (signerInfos.size() != 1)
                throw new IllegalArgumentException(MessageLocalization.getComposedMessage("this.pkcs.7.object.has.multiple.signerinfos.only.one.is.supported.at.this.time"));
            ASN1Sequence signerInfo = (ASN1Sequence)signerInfos.getObjectAt(0);
            // the positions that we care are
            //     0 - version
            //     1 - the signing certificate issuer and serial number
            //     2 - the digest algorithm
            //     3 or 4 - digestEncryptionAlgorithm
            //     4 or 5 - encryptedDigest
            signerversion = ((ASN1Integer)signerInfo.getObjectAt(0)).getValue().intValue();
            // Get the signing certificate
            ASN1Sequence issuerAndSerialNumber = (ASN1Sequence)signerInfo.getObjectAt(1);
            X509Principal issuer = new X509Principal(issuerAndSerialNumber.getObjectAt(0).toASN1Primitive().getEncoded());
            BigInteger serialNumber = ((ASN1Integer)issuerAndSerialNumber.getObjectAt(1)).getValue();
            for (Object element : certs) {
                X509Certificate cert = (X509Certificate)element;
                if (cert.getIssuerDN().equals(issuer) && serialNumber.equals(cert.getSerialNumber())) {
                    signCert = cert;
                    break;
                }
            }
            if (signCert == null) {
                throw new IllegalArgumentException(MessageLocalization.getComposedMessage("can.t.find.signing.certificate.with.serial.1",
                    issuer.getName() + " / " + serialNumber.toString(16)));
            }
            signCertificateChain();
            digestAlgorithmOid = ((ASN1ObjectIdentifier)((ASN1Sequence)signerInfo.getObjectAt(2)).getObjectAt(0)).getId();
            next = 3;
            boolean foundCades = false;
            if (signerInfo.getObjectAt(next) instanceof ASN1TaggedObject) {
                ASN1TaggedObject tagsig = (ASN1TaggedObject)signerInfo.getObjectAt(next);
                ASN1Set sseq = ASN1Set.getInstance(tagsig, false);
                sigAttr = sseq.getEncoded();
                // maybe not necessary, but we use the following line as fallback:
                sigAttrDer = sseq.getEncoded(ASN1Encoding.DER);

                for (int k = 0; k < sseq.size(); ++k) {
                    ASN1Sequence seq2 = (ASN1Sequence)sseq.getObjectAt(k);
                    String idSeq2 = ((ASN1ObjectIdentifier)seq2.getObjectAt(0)).getId();
                    if (idSeq2.equals(SecurityIDs.ID_MESSAGE_DIGEST)) {
                        ASN1Set set = (ASN1Set)seq2.getObjectAt(1);
                        digestAttr = ((ASN1OctetString)set.getObjectAt(0)).getOctets();
                    }
                    else if (idSeq2.equals(SecurityIDs.ID_ADBE_REVOCATION)) {
                        ASN1Set setout = (ASN1Set)seq2.getObjectAt(1);
                        ASN1Sequence seqout = (ASN1Sequence)setout.getObjectAt(0);
                        for (int j = 0; j < seqout.size(); ++j) {
                            ASN1TaggedObject tg = (ASN1TaggedObject)seqout.getObjectAt(j);
                            if (tg.getTagNo() == 0) {
                                ASN1Sequence seqin = (ASN1Sequence)tg.getObject();
                                findCRL(seqin);
                            }
                            if (tg.getTagNo() == 1) {
                                ASN1Sequence seqin = (ASN1Sequence)tg.getObject();
                                findOcsp(seqin);
                            }
                        }
                    }
                    else if (isCades && idSeq2.equals(SecurityIDs.ID_AA_SIGNING_CERTIFICATE_V1)) {
                        ASN1Set setout = (ASN1Set)seq2.getObjectAt(1);
                        ASN1Sequence seqout = (ASN1Sequence)setout.getObjectAt(0);
                        SigningCertificate sv2 = SigningCertificate.getInstance(seqout);
                        ESSCertID[] cerv2m = sv2.getCerts();
                        ESSCertID cerv2 = cerv2m[0];
                        byte[] enc2 = signCert.getEncoded();
                        MessageDigest m2 = new BouncyCastleDigest().getMessageDigest("SHA-1");
                        byte[] signCertHash = m2.digest(enc2);
                        byte[] hs2 = cerv2.getCertHash();
                        if (!Arrays.equals(signCertHash, hs2))
                            throw new IllegalArgumentException("Signing certificate doesn't match the ESS information.");
                        foundCades = true;
                    }
                    else if (isCades && idSeq2.equals(SecurityIDs.ID_AA_SIGNING_CERTIFICATE_V2)) {
                        ASN1Set setout = (ASN1Set)seq2.getObjectAt(1);
                        ASN1Sequence seqout = (ASN1Sequence)setout.getObjectAt(0);
                        SigningCertificateV2 sv2 = SigningCertificateV2.getInstance(seqout);
                        ESSCertIDv2[] cerv2m = sv2.getCerts();
                        ESSCertIDv2 cerv2 = cerv2m[0];
                        AlgorithmIdentifier ai2 = cerv2.getHashAlgorithm();
                        byte[] enc2 = signCert.getEncoded();
                        MessageDigest m2 = new BouncyCastleDigest().getMessageDigest(DigestAlgorithms.getDigest(ai2.getAlgorithm().getId()));
                        byte[] signCertHash = m2.digest(enc2);
                        byte[] hs2 = cerv2.getCertHash();
                        if (!Arrays.equals(signCertHash, hs2))
                            throw new IllegalArgumentException("Signing certificate doesn't match the ESS information.");
                        foundCades = true;
                    }
                }
                if (digestAttr == null)
                    throw new IllegalArgumentException(MessageLocalization.getComposedMessage("authenticated.attribute.is.missing.the.digest"));
                ++next;
            }
            if (isCades && !foundCades)
                throw new IllegalArgumentException("CAdES ESS information missing.");
            digestEncryptionAlgorithmOid = ((ASN1ObjectIdentifier)((ASN1Sequence)signerInfo.getObjectAt(next++)).getObjectAt(0)).getId();
            digest = ((ASN1OctetString)signerInfo.getObjectAt(next++)).getOctets();
            if (next < signerInfo.size() && signerInfo.getObjectAt(next) instanceof ASN1TaggedObject) {
                ASN1TaggedObject taggedObject = (ASN1TaggedObject) signerInfo.getObjectAt(next);
                ASN1Set unat = ASN1Set.getInstance(taggedObject, false);
                AttributeTable attble = new AttributeTable(unat);
                Attribute ts = attble.get(PKCSObjectIdentifiers.id_aa_signatureTimeStampToken);
                if (ts != null && ts.getAttrValues().size() > 0) {
                    ASN1Set attributeValues = ts.getAttrValues();
                    ASN1Sequence tokenSequence = ASN1Sequence.getInstance(attributeValues.getObjectAt(0));
                    ContentInfo contentInfo = new ContentInfo(tokenSequence);
                    this.timeStampToken = new TimeStampToken(contentInfo);
                }
            }
            if (isTsp) {
                ContentInfo contentInfoTsp = new ContentInfo(signedData);
                this.timeStampToken = new TimeStampToken(contentInfoTsp);
                TimeStampTokenInfo info = timeStampToken.getTimeStampInfo();
                String algOID = info.getMessageImprintAlgOID().getId();
                messageDigest = DigestAlgorithms.getMessageDigestFromOid(algOID, null);
            }
            else {
                if (RSAdata != null || digestAttr != null) {
                	if (PdfName.ADBE_PKCS7_SHA1.equals(getFilterSubtype())) {
                		messageDigest = DigestAlgorithms.getMessageDigest("SHA1", provider);
                	}
                	else {
                		messageDigest = DigestAlgorithms.getMessageDigest(getHashAlgorithm(), provider);
                	}
                	encContDigest = DigestAlgorithms.getMessageDigest(getHashAlgorithm(), provider);
                }
                sig = initSignature(signCert.getPublicKey());
            }
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    // Encryption provider

    /** The encryption provider, e.g. "BC" if you use BouncyCastle. */
    private String provider;

    // Signature info

    private SignaturePolicyIdentifier signaturePolicyIdentifier;

    /** Holds value of property signName. */
    private String signName;

    /** Holds value of property reason. */
    private String reason;

    /** Holds value of property location. */
    private String location;

    /** Holds value of property signDate. */
    private Calendar signDate;

    public void setSignaturePolicy(SignaturePolicyInfo signaturePolicy) {
        this.signaturePolicyIdentifier = signaturePolicy.toSignaturePolicyIdentifier();
    }

    public void setSignaturePolicy(SignaturePolicyIdentifier signaturePolicy) {
        this.signaturePolicyIdentifier = signaturePolicy;
    }

    /**
     * Getter for property sigName.
     * @return Value of property sigName.
     */
    public String getSignName() {
        return this.signName;
    }

    /**
     * Setter for property sigName.
     * @param signName New value of property sigName.
     */
    public void setSignName(String signName) {
        this.signName = signName;
    }

    /**
     * Getter for property reason.
     * @return Value of property reason.
     */
    public String getReason() {
        return this.reason;
    }

    /**
     * Setter for property reason.
     * @param reason New value of property reason.
     */
    public void setReason(String reason) {
        this.reason = reason;
    }

    /**
     * Getter for property location.
     * @return Value of property location.
     */
    public String getLocation() {
        return this.location;
    }

    /**
     * Setter for property location.
     * @param location New value of property location.
     */
    public void setLocation(String location) {
        this.location = location;
    }

    /**
     * Getter for property signDate.
     * @return Value of property signDate.
     */
    public Calendar getSignDate() {
        Calendar dt = getTimeStampDate();
        if (dt == null)
            return this.signDate;
        else
            return dt;
    }

    /**
     * Setter for property signDate.
     * @param signDate New value of property signDate.
     */
    public void setSignDate(Calendar signDate) {
        this.signDate = signDate;
    }

	// version info

	/** Version of the PKCS#7 object */
    private int version = 1;

    /** Version of the PKCS#7 "SignerInfo" object. */
    private int signerversion = 1;

    /**
     * Get the version of the PKCS#7 object.
     * @return the version of the PKCS#7 object.
     */
    public int getVersion() {
        return version;
    }

    /**
     * Get the version of the PKCS#7 "SignerInfo" object.
     * @return the version of the PKCS#7 "SignerInfo" object.
     */
    public int getSigningInfoVersion() {
        return signerversion;
    }

    // Message digest algorithm

    /** The ID of the digest algorithm, e.g. "2.16.840.1.101.3.4.2.1". */
    private String digestAlgorithmOid;

    /** The object that will create the digest */
    private MessageDigest messageDigest;

    /** The digest algorithms */
    private Set<String> digestalgos;

    /** The digest attributes */
    private byte[] digestAttr;

    private PdfName filterSubtype;

    /**
     * Getter for the ID of the digest algorithm, e.g. "2.16.840.1.101.3.4.2.1"
     */
    public String getDigestAlgorithmOid() {
        return digestAlgorithmOid;
    }

    /**
     * Returns the name of the digest algorithm, e.g. "SHA256".
     * @return the digest algorithm name, e.g. "SHA256"
     */
    public String getHashAlgorithm() {
        return DigestAlgorithms.getDigest(digestAlgorithmOid);
    }

    // Encryption algorithm

    /** The encryption algorithm. */
    private String digestEncryptionAlgorithmOid;

    /**
     * Getter for the digest encryption algorithm
     */
    public String getDigestEncryptionAlgorithmOid() {
        return digestEncryptionAlgorithmOid;
    }

    /**
     * Get the algorithm used to calculate the message digest, e.g. "SHA1withRSA".
     * @return the algorithm used to calculate the message digest
     */
    public String getDigestAlgorithm() {
    	return getHashAlgorithm() + "with" + getEncryptionAlgorithm();
    }

    /*
     *	DIGITAL SIGNATURE CREATION
     */

    private ExternalDigest interfaceDigest;
    // The signature is created externally

    /** The signed digest if created outside this class */
    private byte externalDigest[];

    /** External RSA data */
    private byte externalRSAdata[];

    /**
     * Sets the digest/signature to an external calculated value.
     * @param digest the digest. This is the actual signature
     * @param RSAdata the extra data that goes into the data tag in PKCS#7
     * @param digestEncryptionAlgorithm the encryption algorithm. It may must be <CODE>null</CODE> if the <CODE>digest</CODE>
     * is also <CODE>null</CODE>. If the <CODE>digest</CODE> is not <CODE>null</CODE>
     * then it may be "RSA" or "DSA"
     */
    public void setExternalDigest(byte digest[], byte RSAdata[], String digestEncryptionAlgorithm) {
        externalDigest = digest;
        externalRSAdata = RSAdata;
        if (digestEncryptionAlgorithm != null) {
            if (digestEncryptionAlgorithm.equals("RSA")) {
                this.digestEncryptionAlgorithmOid = SecurityIDs.ID_RSA;
            }
            else if (digestEncryptionAlgorithm.equals("DSA")) {
                this.digestEncryptionAlgorithmOid = SecurityIDs.ID_DSA;
            }
            else if (digestEncryptionAlgorithm.equals("ECDSA")) {
                this.digestEncryptionAlgorithmOid = SecurityIDs.ID_ECDSA;
            }
            else if(digestEncryptionAlgorithm.equals("SM2")) {
                this.digestEncryptionAlgorithmOid = GMObjectIdentifiers.sm2sign_with_sm3.getId();
            }
            else if (digestEncryptionAlgorithm.equals("SM3")) { // sm3
                this.digestEncryptionAlgorithmOid = GMObjectIdentifiers.sm3.getId();
            }
            else
                throw new ExceptionConverter(new NoSuchAlgorithmException(MessageLocalization.getComposedMessage("unknown.key.algorithm.1", digestEncryptionAlgorithm)));
        }
    }

    // The signature is created internally

    /** Class from the Java SDK that provides the functionality of a digital signature algorithm. */
    private Signature sig;

    /** The signed digest as calculated by this class (or extracted from an existing PDF) */
    private byte[] digest;

    /** The RSA data */
    private byte[] RSAdata;

    // Signing functionality.

    private Signature initSignature(PrivateKey key) throws NoSuchAlgorithmException, NoSuchProviderException, InvalidKeyException {
    	Signature signature;
        if (provider == null)
            signature = Signature.getInstance(getDigestAlgorithm());
        else
            signature = Signature.getInstance(getDigestAlgorithm(), provider);
        signature.initSign(key);
        return signature;
    }

    private Signature initSignature(PublicKey key) throws NoSuchAlgorithmException, NoSuchProviderException, InvalidKeyException {
    	String digestAlgorithm = getDigestAlgorithm();
    	if (PdfName.ADBE_X509_RSA_SHA1.equals(getFilterSubtype()))
    		digestAlgorithm = "SHA1withRSA";
    	Signature signature;
        if (provider == null)
            signature = Signature.getInstance(digestAlgorithm);
        else
            signature = Signature.getInstance(digestAlgorithm, provider);

        signature.initVerify(key);
        return signature;
    }

    /**
     * Update the digest with the specified bytes.
     * This method is used both for signing and verifying
     * @param buf the data buffer
     * @param off the offset in the data buffer
     * @param len the data length
     * @throws SignatureException on error
     */
    public void update(byte[] buf, int off, int len) throws SignatureException {
        if (RSAdata != null || digestAttr != null || isTsp)
            messageDigest.update(buf, off, len);
        else
            sig.update(buf, off, len);
    }

    // adbe.x509.rsa_sha1 (PKCS#1)

    /**
     * Gets the bytes for the PKCS#1 object.
     * @return a byte array
     */
    public byte[] getEncodedPKCS1() {
        try {
            if (externalDigest != null)
                digest = externalDigest;
            else
                digest = sig.sign();
            ByteArrayOutputStream   bOut = new ByteArrayOutputStream();

            ASN1OutputStream dout = new ASN1OutputStream(bOut);
            dout.writeObject(new DEROctetString(digest));
            dout.close();

            return bOut.toByteArray();
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    // other subfilters (PKCS#7)

    /**
     * Gets the bytes for the PKCS7SignedData object.
     * @return the bytes for the PKCS7SignedData object
     */
    public byte[] getEncodedPKCS7() {
        return getEncodedPKCS7(null, null, null, null, CryptoStandard.CMS);
    }

    /**
     * Gets the bytes for the PKCS7SignedData object. Optionally the authenticatedAttributes
     * in the signerInfo can also be set. If either of the parameters is <CODE>null</CODE>, none will be used.
     * @param secondDigest the digest in the authenticatedAttributes
     * @return the bytes for the PKCS7SignedData object
     */
    public byte[] getEncodedPKCS7(byte secondDigest[]) {
        return getEncodedPKCS7(secondDigest, null, null, null, CryptoStandard.CMS);
    }

    /**
     * Gets the bytes for the PKCS7SignedData object. Optionally the authenticatedAttributes
     * in the signerInfo can also be set, OR a time-stamp-authority client
     * may be provided.
     * @param secondDigest the digest in the authenticatedAttributes
     * @param tsaClient TSAClient - null or an optional time stamp authority client
     * @return byte[] the bytes for the PKCS7SignedData object
     * @since	2.1.6
     */
    public byte[] getEncodedPKCS7(byte secondDigest[], TSAClient tsaClient, byte[] ocsp, Collection<byte[]> crlBytes, CryptoStandard sigtype) {
        try {
            if (externalDigest != null) {
                digest = externalDigest;
                if (RSAdata != null)
                    RSAdata = externalRSAdata;
            }
            else if (externalRSAdata != null && RSAdata != null) {
                RSAdata = externalRSAdata;
                sig.update(RSAdata);
                digest = sig.sign();
            }
            else {
                if (RSAdata != null) {
                    RSAdata = messageDigest.digest();
                    sig.update(RSAdata);
                }
                digest = sig.sign();
            }

            // Create the set of Hash algorithms
            ASN1EncodableVector digestAlgorithms = new ASN1EncodableVector();
            for (Object element : digestalgos) {
                ASN1EncodableVector algos = new ASN1EncodableVector();
                algos.add(new ASN1ObjectIdentifier((String)element));
                algos.add(DERNull.INSTANCE);
                digestAlgorithms.add(new DERSequence(algos));
            }

            // Create the contentInfo.
            ASN1EncodableVector v = new ASN1EncodableVector();
            v.add(new ASN1ObjectIdentifier(SecurityIDs.ID_PKCS7_DATA));
            if (RSAdata != null)
                v.add(new DERTaggedObject(0, new DEROctetString(RSAdata)));
            DERSequence contentinfo = new DERSequence(v);

            // Get all the certificates
            //
            v = new ASN1EncodableVector();
            for (Object element : certs) {
                ASN1InputStream tempstream = new ASN1InputStream(new ByteArrayInputStream(((X509Certificate)element).getEncoded()));
                v.add(tempstream.readObject());
            }

            DERSet dercertificates = new DERSet(v);

            // Create signerinfo structure.
            //
            ASN1EncodableVector signerinfo = new ASN1EncodableVector();

            // Add the signerInfo version
            //
            signerinfo.add(new ASN1Integer(signerversion));

            v = new ASN1EncodableVector();
            v.add(CertificateInfo.getIssuer(signCert.getTBSCertificate()));
            v.add(new ASN1Integer(signCert.getSerialNumber()));
            signerinfo.add(new DERSequence(v));

            // Add the digestAlgorithm
            v = new ASN1EncodableVector();
            v.add(new ASN1ObjectIdentifier(digestAlgorithmOid));
            v.add(new DERNull());
            signerinfo.add(new DERSequence(v));

            // add the authenticated attribute if present
            if (secondDigest != null) {
                signerinfo.add(new DERTaggedObject(false, 0, getAuthenticatedAttributeSet(secondDigest, ocsp, crlBytes, sigtype)));
            }
            // Add the digestEncryptionAlgorithm
            v = new ASN1EncodableVector();
            v.add(new ASN1ObjectIdentifier(digestEncryptionAlgorithmOid));
            v.add(new DERNull());
            signerinfo.add(new DERSequence(v));

            // Add the digest
            signerinfo.add(new DEROctetString(digest));

            // When requested, go get and add the timestamp. May throw an exception.
            // Added by Martin Brunecky, 07/12/2007 folowing Aiken Sam, 2006-11-15
            // Sam found Adobe expects time-stamped SHA1-1 of the encrypted digest
            if (tsaClient != null) {
                byte[] tsImprint = tsaClient.getMessageDigest().digest(digest);
                byte[] tsToken = tsaClient.getTimeStampToken(tsImprint);
                if (tsToken != null) {
                    ASN1EncodableVector unauthAttributes = buildUnauthenticatedAttributes(tsToken);
                    if (unauthAttributes != null) {
                        signerinfo.add(new DERTaggedObject(false, 1, new DERSet(unauthAttributes)));
                    }
                }
            }

            // Finally build the body out of all the components above
            ASN1EncodableVector body = new ASN1EncodableVector();
            body.add(new ASN1Integer(version));
            body.add(new DERSet(digestAlgorithms));
            body.add(contentinfo);
            body.add(new DERTaggedObject(false, 0, dercertificates));

            // Only allow one signerInfo
            body.add(new DERSet(new DERSequence(signerinfo)));

            // Now we have the body, wrap it in it's PKCS7Signed shell
            // and return it
            //
            ASN1EncodableVector whole = new ASN1EncodableVector();
            whole.add(new ASN1ObjectIdentifier(SecurityIDs.ID_PKCS7_SIGNED_DATA));
            whole.add(new DERTaggedObject(0, new DERSequence(body)));

            ByteArrayOutputStream   bOut = new ByteArrayOutputStream();

            ASN1OutputStream dout = new ASN1OutputStream(bOut);
            dout.writeObject(new DERSequence(whole));
            dout.close();

            return bOut.toByteArray();
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    /**
     * Added by Aiken Sam, 2006-11-15, modifed by Martin Brunecky 07/12/2007
     * to start with the timeStampToken (signedData 1.2.840.113549.1.7.2).
     * Token is the TSA response without response status, which is usually
     * handled by the (vendor supplied) TSA request/response interface).
     * @param timeStampToken byte[] - time stamp token, DER encoded signedData
     * @return ASN1EncodableVector
     * @throws IOException
     */
    private ASN1EncodableVector buildUnauthenticatedAttributes(byte[] timeStampToken)  throws IOException {
        if (timeStampToken == null)
            return null;

        // @todo: move this together with the rest of the defintions
        String ID_TIME_STAMP_TOKEN = "1.2.840.113549.1.9.16.2.14"; // RFC 3161 id-aa-timeStampToken

        ASN1InputStream tempstream = new ASN1InputStream(new ByteArrayInputStream(timeStampToken));
        ASN1EncodableVector unauthAttributes = new ASN1EncodableVector();

        ASN1EncodableVector v = new ASN1EncodableVector();
        v.add(new ASN1ObjectIdentifier(ID_TIME_STAMP_TOKEN)); // id-aa-timeStampToken
        ASN1Sequence seq = (ASN1Sequence) tempstream.readObject();
        v.add(new DERSet(seq));

        unauthAttributes.add(new DERSequence(v));
        return unauthAttributes;
     }

    // Authenticated attributes

    /**
     * When using authenticatedAttributes the authentication process is different.
     * The document digest is generated and put inside the attribute. The signing is done over the DER encoded
     * authenticatedAttributes. This method provides that encoding and the parameters must be
     * exactly the same as in {@link #getEncodedPKCS7(byte[])}.
     * <p>
     * A simple example:
     * <p>
     * <pre>
     * Calendar cal = Calendar.getInstance();
     * PdfPKCS7 pk7 = new PdfPKCS7(key, chain, null, "SHA1", null, false);
     * MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
     * byte buf[] = new byte[8192];
     * int n;
     * InputStream inp = sap.getRangeStream();
     * while ((n = inp.read(buf)) &gt; 0) {
     *    messageDigest.update(buf, 0, n);
     * }
     * byte hash[] = messageDigest.digest();
     * byte sh[] = pk7.getAuthenticatedAttributeBytes(hash, cal);
     * pk7.update(sh, 0, sh.length);
     * byte sg[] = pk7.getEncodedPKCS7(hash, cal);
     * </pre>
     * @param secondDigest the content digest
     * @return the byte array representation of the authenticatedAttributes ready to be signed
     */
    public byte[] getAuthenticatedAttributeBytes(byte secondDigest[], byte[] ocsp, Collection<byte[]> crlBytes, CryptoStandard sigtype) {
        try {
            return getAuthenticatedAttributeSet(secondDigest, ocsp, crlBytes, sigtype).getEncoded(ASN1Encoding.DER);
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    /**
     * This method provides that encoding and the parameters must be
     * exactly the same as in {@link #getEncodedPKCS7(byte[])}.
     *
     * @param secondDigest the content digest
     * @return the byte array representation of the authenticatedAttributes ready to be signed
     */
    private DERSet getAuthenticatedAttributeSet(byte secondDigest[], byte[] ocsp, Collection<byte[]> crlBytes, CryptoStandard sigtype) {
        try {
            ASN1EncodableVector attribute = new ASN1EncodableVector();
            ASN1EncodableVector v = new ASN1EncodableVector();
            v.add(new ASN1ObjectIdentifier(SecurityIDs.ID_CONTENT_TYPE));
            v.add(new DERSet(new ASN1ObjectIdentifier(SecurityIDs.ID_PKCS7_DATA)));
            attribute.add(new DERSequence(v));
            v = new ASN1EncodableVector();
            v.add(new ASN1ObjectIdentifier(SecurityIDs.ID_MESSAGE_DIGEST));
            v.add(new DERSet(new DEROctetString(secondDigest)));
            attribute.add(new DERSequence(v));
            boolean haveCrl = false;
            if (crlBytes != null) {
                for (byte[] bCrl : crlBytes) {
                    if (bCrl != null) {
                        haveCrl = true;
                        break;
                    }
                }
            }
            if (ocsp != null || haveCrl) {
                v = new ASN1EncodableVector();
                v.add(new ASN1ObjectIdentifier(SecurityIDs.ID_ADBE_REVOCATION));

                ASN1EncodableVector revocationV = new ASN1EncodableVector();

                if (haveCrl) {
                    ASN1EncodableVector v2 = new ASN1EncodableVector();
                    for (byte[] bCrl : crlBytes) {
                        if (bCrl == null)
                            continue;
                        ASN1InputStream t = new ASN1InputStream(new ByteArrayInputStream(bCrl));
                        v2.add(t.readObject());
                    }
                    revocationV.add(new DERTaggedObject(true, 0, new DERSequence(v2)));
                }

                if (ocsp != null) {
	                DEROctetString doctet = new DEROctetString(ocsp);
	                ASN1EncodableVector vo1 = new ASN1EncodableVector();
	                ASN1EncodableVector v2 = new ASN1EncodableVector();
	                v2.add(OCSPObjectIdentifiers.id_pkix_ocsp_basic);
	                v2.add(doctet);
	                ASN1Enumerated den = new ASN1Enumerated(0);
	                ASN1EncodableVector v3 = new ASN1EncodableVector();
	                v3.add(den);
	                v3.add(new DERTaggedObject(true, 0, new DERSequence(v2)));
	                vo1.add(new DERSequence(v3));
	                revocationV.add(new DERTaggedObject(true, 1, new DERSequence(vo1)));
                }

                v.add(new DERSet(new DERSequence(revocationV)));
                attribute.add(new DERSequence(v));
            }
            if (sigtype == CryptoStandard.CADES) {
                v = new ASN1EncodableVector();
                v.add(new ASN1ObjectIdentifier(SecurityIDs.ID_AA_SIGNING_CERTIFICATE_V2));

                ASN1EncodableVector aaV2 = new ASN1EncodableVector();
                String sha256Oid = DigestAlgorithms.getAllowedDigests(DigestAlgorithms.SHA256);

                // If we look into X.690-0207, clause 11.5, we can see that using DER all the components of a sequence having
                // default values shall not be included. According to RFC 5035, 5.4.1.1, definition of ESSCertIDv2, default
                // AlgorithmIdentifier is sha256.
                if (!sha256Oid.equals(digestAlgorithmOid)) {
                    AlgorithmIdentifier algoId = new AlgorithmIdentifier(new ASN1ObjectIdentifier(digestAlgorithmOid));
                    aaV2.add(algoId);
                }

                MessageDigest md = interfaceDigest.getMessageDigest(getHashAlgorithm());
                byte[] dig = md.digest(signCert.getEncoded());
                aaV2.add(new DEROctetString(dig));

                v.add(new DERSet(new DERSequence(new DERSequence(new DERSequence(aaV2)))));
                attribute.add(new DERSequence(v));
            }

            if (signaturePolicyIdentifier != null) {
                attribute.add(new Attribute(PKCSObjectIdentifiers.id_aa_ets_sigPolicyId, new DERSet(signaturePolicyIdentifier)));
            }

            return new DERSet(attribute);
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }
    /*
     *	DIGITAL SIGNATURE VERIFICATION
     */
    /** Signature attributes */
    private byte[] sigAttr;
    /** Signature attributes (maybe not necessary, but we use it as fallback) */
    private byte[] sigAttrDer;

    /** encrypted digest */
    private MessageDigest encContDigest; // Stefan Santesson

    /** Indicates if a signature has already been verified */
    private boolean verified;

    /** The result of the verification */
    private boolean verifyResult;


    // verification

    /**
     * Verify the digest.
     * @throws SignatureException on error
     * @return <CODE>true</CODE> if the signature checks out, <CODE>false</CODE> otherwise
     * @throws java.security.GeneralSecurityException
     */
    public boolean verify() throws GeneralSecurityException {
        if (verified)
            return verifyResult;
        if (isTsp) {
            TimeStampTokenInfo info = timeStampToken.getTimeStampInfo();
            MessageImprint imprint = info.toASN1Structure().getMessageImprint();
            byte[] md = messageDigest.digest();
            byte[] imphashed = imprint.getHashedMessage();
            verifyResult = Arrays.equals(md, imphashed);
        }
        else {
            if (sigAttr != null || sigAttrDer != null) {
                final byte [] msgDigestBytes = messageDigest.digest();
                boolean verifyRSAdata = true;
                // Stefan Santesson fixed a bug, keeping the code backward compatible
                boolean encContDigestCompare = false;
                if (RSAdata != null) {
                    verifyRSAdata = Arrays.equals(msgDigestBytes, RSAdata);
                    encContDigest.update(RSAdata);
                    encContDigestCompare = Arrays.equals(encContDigest.digest(), digestAttr);
                }
                boolean absentEncContDigestCompare = Arrays.equals(msgDigestBytes, digestAttr);
                boolean concludingDigestCompare = absentEncContDigestCompare || encContDigestCompare;
                boolean sigVerify = verifySigAttributes(sigAttr) || verifySigAttributes(sigAttrDer);
                verifyResult = concludingDigestCompare && sigVerify && verifyRSAdata;
            }
            else {
                if (RSAdata != null)
                    sig.update(messageDigest.digest());
                verifyResult = sig.verify(digest);
            }
        }
        verified = true;
        return verifyResult;
    }

    private boolean verifySigAttributes(byte[] attr) throws GeneralSecurityException {
    	Signature signature = initSignature(signCert.getPublicKey());
    	signature.update(attr);
    	return signature.verify(digest);
    }

    /**
     * Checks if the timestamp refers to this document.
     * @return true if it checks false otherwise
     * @throws GeneralSecurityException on error
     * @since	2.1.6
     */
    public boolean verifyTimestampImprint() throws GeneralSecurityException {
        if (timeStampToken == null)
            return false;
        TimeStampTokenInfo info = timeStampToken.getTimeStampInfo();
        MessageImprint imprint = info.toASN1Structure().getMessageImprint();
        String algOID = info.getMessageImprintAlgOID().getId();
        byte[] md = new BouncyCastleDigest().getMessageDigest(DigestAlgorithms.getDigest(algOID)).digest(digest);
        byte[] imphashed = imprint.getHashedMessage();
        boolean res = Arrays.equals(md, imphashed);
        return res;
    }

	// Certificates

    /** All the X.509 certificates in no particular order. */
    private Collection<Certificate> certs;

    /** All the X.509 certificates used for the main signature. */
    private Collection<Certificate> signCerts;

    /** The X.509 certificate that is used to sign the digest. */
    private X509Certificate signCert;

    /**
     * Get all the X.509 certificates associated with this PKCS#7 object in no particular order.
     * Other certificates, from OCSP for example, will also be included.
     * @return the X.509 certificates associated with this PKCS#7 object
     */
    public Certificate[] getCertificates() {
        return certs.toArray(new X509Certificate[certs.size()]);
    }

    /**
     * Get the X.509 sign certificate chain associated with this PKCS#7 object.
     * Only the certificates used for the main signature will be returned, with
     * the signing certificate first.
     * @return the X.509 certificates associated with this PKCS#7 object
     * @since	2.1.6
     */
    public Certificate[] getSignCertificateChain() {
        return signCerts.toArray(new X509Certificate[signCerts.size()]);
    }

    /**
     * Get the X.509 certificate actually used to sign the digest.
     * @return the X.509 certificate actually used to sign the digest
     */
    public X509Certificate getSigningCertificate() {
        return signCert;
    }

    /**
     * Helper method that creates the collection of certificates
     * used for the main signature based on the complete list
     * of certificates and the sign certificate.
     */
    private void signCertificateChain() {
        ArrayList<Certificate> cc = new ArrayList<Certificate>();
        cc.add(signCert);
        ArrayList<Certificate> oc = new ArrayList<Certificate>(certs);
        for (int k = 0; k < oc.size(); ++k) {
            if (signCert.equals(oc.get(k))) {
                oc.remove(k);
                --k;
                continue;
            }
        }
        boolean found = true;
        while (found) {
            X509Certificate v = (X509Certificate)cc.get(cc.size() - 1);
            found = false;
            for (int k = 0; k < oc.size(); ++k) {
            	X509Certificate issuer = (X509Certificate)oc.get(k);
                try {
                    if (provider == null)
                        v.verify(issuer.getPublicKey());
                    else
                        v.verify(issuer.getPublicKey(), provider);
                    found = true;
                    cc.add(oc.get(k));
                    oc.remove(k);
                    break;
                }
                catch (Exception e) {
                }
            }
        }
        signCerts = cc;
    }

	// Certificate Revocation Lists

    private Collection<CRL> crls;

    /**
     * Get the X.509 certificate revocation lists associated with this PKCS#7 object
     * @return the X.509 certificate revocation lists associated with this PKCS#7 object
     */
    public Collection<CRL> getCRLs() {
        return crls;
    }

    /**
     * Helper method that tries to construct the CRLs.
     */
    private void findCRL(ASN1Sequence seq) {
        try {
            crls = new ArrayList<CRL>();
            for (int k = 0; k < seq.size(); ++k) {
                ByteArrayInputStream ar = new ByteArrayInputStream(seq.getObjectAt(k).toASN1Primitive().getEncoded(ASN1Encoding.DER));
                CertificateFactory cf = CertificateFactory.getInstance("X.509");
                X509CRL crl = (X509CRL)cf.generateCRL(ar);
                crls.add(crl);
            }
        }
        catch (Exception ex) {
            // ignore
        }
    }

    // Online Certificate Status Protocol

    /** BouncyCastle BasicOCSPResp */
    private BasicOCSPResp basicResp;

    /**
     * Gets the OCSP basic response if there is one.
     * @return the OCSP basic response or null
     * @since	2.1.6
     */
    public BasicOCSPResp getOcsp() {
        return basicResp;
    }

    /**
     * Checks if OCSP revocation refers to the document signing certificate.
     * @return true if it checks, false otherwise
     * @since	2.1.6
     */
    public boolean isRevocationValid() {
        if (basicResp == null)
            return false;
        if (signCerts.size() < 2)
            return false;
        try {
            X509Certificate[] cs = (X509Certificate[])getSignCertificateChain();
            SingleResp sr = basicResp.getResponses()[0];
            CertificateID cid = sr.getCertID();
            DigestCalculator digestalg = new JcaDigestCalculatorProviderBuilder().build().get(new AlgorithmIdentifier(cid.getHashAlgOID(), DERNull.INSTANCE));
            X509Certificate sigcer = getSigningCertificate();
            X509Certificate isscer = cs[1];
            CertificateID tis = new CertificateID(
                digestalg, new JcaX509CertificateHolder(isscer), sigcer.getSerialNumber());
            return tis.equals(cid);
        }
        catch (Exception ex) {
        }
        return false;
    }

    /**
     * Helper method that creates the BasicOCSPResp object.
     * @param seq
     * @throws IOException
     */
    private void findOcsp(ASN1Sequence seq) throws IOException {
        basicResp = null;
        boolean ret = false;
        while (true) {
            if (seq.getObjectAt(0) instanceof ASN1ObjectIdentifier
                && ((ASN1ObjectIdentifier)seq.getObjectAt(0)).getId().equals(OCSPObjectIdentifiers.id_pkix_ocsp_basic.getId())) {
                break;
            }
            ret = true;
            for (int k = 0; k < seq.size(); ++k) {
                if (seq.getObjectAt(k) instanceof ASN1Sequence) {
                    seq = (ASN1Sequence)seq.getObjectAt(0);
                    ret = false;
                    break;
                }
                if (seq.getObjectAt(k) instanceof ASN1TaggedObject) {
                    ASN1TaggedObject tag = (ASN1TaggedObject)seq.getObjectAt(k);
                    if (tag.getObject() instanceof ASN1Sequence) {
                        seq = (ASN1Sequence)tag.getObject();
                        ret = false;
                        break;
                    }
                    else
                        return;
                }
            }
            if (ret)
                return;
        }
        ASN1OctetString os = (ASN1OctetString)seq.getObjectAt(1);
        ASN1InputStream inp = new ASN1InputStream(os.getOctets());
        BasicOCSPResponse resp = BasicOCSPResponse.getInstance(inp.readObject());
        basicResp = new BasicOCSPResp(resp);
    }

    // Time Stamps

    /** True if there's a PAdES LTV time stamp. */
    private boolean isTsp;

    /** True if it's a CAdES signature type. */
    private boolean isCades;

    /** BouncyCastle TimeStampToken. */
    private TimeStampToken timeStampToken;

    /**
     * Check if it's a PAdES-LTV time stamp.
     * @return true if it's a PAdES-LTV time stamp, false otherwise
     */
    public boolean isTsp() {
        return isTsp;
    }

    /**
     * Gets the timestamp token if there is one.
     * @return the timestamp token or null
     * @since	2.1.6
     */
    public TimeStampToken getTimeStampToken() {
    	return timeStampToken;
    }

    /**
     * Gets the timestamp date
     * @return	a date
     * @since	2.1.6
     */
    public Calendar getTimeStampDate() {
        if (timeStampToken == null)
            return null;
        Calendar cal = new GregorianCalendar();
        Date date = timeStampToken.getTimeStampInfo().getGenTime();
        cal.setTime(date);
        return cal;
    }

    /**
     * Returns the filter subtype.
     */
    public PdfName getFilterSubtype() {
    	return filterSubtype;
    }

    /**
     * Returns the encryption algorithm
     * @return	the name of an encryption algorithm
     */
    public String getEncryptionAlgorithm() {
        String encryptAlgo = EncryptionAlgorithms.getAlgorithm(digestEncryptionAlgorithmOid);
        if (encryptAlgo == null)
            encryptAlgo = digestEncryptionAlgorithmOid;
        return encryptAlgo;
    }
}
